The use of acids in the food industry is well known. For example in the making of dry or semi dry sausages, lactic acid producing bacteria has long been used in order improve flavour and conservation of the product. Most often, encapsulated acids are used for controlled release of acid in a food composition. The control-release mechanisms vary with the application. Some applications require a temperature release (when the product is exposed to a given temperature the acid is released; fat/oil coatings), water release (when the product is exposed to water release takes place; water soluble coatings), pH release, and the like. The aim is to protect the encapsulated core from the environment up to the time when it is needed. Different applications require a different level of encapsulation. Typically, for an application where temperature release is required, the quality of the encapsulation is judged by the percentage of release of the product dispersed in water at room temperature. A 90% encapsulation refers to a product releasing 10% (w/w) of core ingredient in the water at room temperature after a given time. Similarly, the release of the food ingredient can be directly measured in the application itself through different analytical methods.
The use of encapsulated food acids in meat was first reported in the early 1960's. At first, the use of glucono delta lactone (GDL) for curing purposes was described in U.S. Pat. No. 2,992,116. Shortly after, in U.S. Pat. Nos. 3,359,120 and 3,560,222, encapsulated food acid was reported to have similar effects. In the same period, patent applications were filed for the production of encapsulated food acids. The processes used were very diverse: from top-spray fluid bed coating to coacervation, and from co-axial extrusion to spray drying techniques.
Lactic acid is widely used in the food industries, such as in the dairy, meat, and bakery industries and in the confectionery industry. Lactic acid is also often reported as being used in a coated form in a food composition. See, for instance, CH 527 570, U.S. Pat. Nos. 4,262,027, and 4,576,825. However, these patents disclose the use of lactic acid in the liquid form, and it is necessary to combine the liquid lactic acid with a solid substrate in order to obtain a solid composition. In CH 527 570, lactic acid is combined with glucose, in U.S. Pat. No. 4,497,845 with a solid carrier, in U.S. Pat. No. 4,511,584 with micro-cellulose or calcium lactate, and in U.S. Pat. Nos. 4,511,592, 4,772,477, and 6,153,236, the lactic acid is platted on calcium lactate. In U.S. Pat. No. 4,576,825, liquid lactic acid is encapsulated using a co-axial-extrusion method.
In all patents where the use of coated lactic acid is reported and where the lactic acid is mixed with another component in order to be solid, the other component does not bring any additional advantages. Its effect is limited to the solidification of lactic acid either by absorption (glucose, starches, micro-cellulose) or by reaction (calcium lactate). The content of lactic acid in these products does not exceed 60% (w/w) usually due to the extra components. Often, the content of lactic acid of the final products presented in these patents does not exceed 50%, and more commonly it does not exceed 30% (w/w). Moreover, the products combined with lactic acid to render it solid can have adverse effects on the application. For example the calcium lactate combined with the lactic acid has a buffering action on the lactic acid. Also, encapsulation of liquid lactic acid requires expensive equipment and the resulting encapsulated liquid lactic acid is expensive and difficult to handle.
Crystalline Lactic acid is described by Schouten et al. (Low Temperature Crystal Structure And Molecular Conformation Of L(+) Lactic Acid, J. Mol. Structure, 323: 165-168 (1994)). Even though crystalline lactic acid had been known, it is difficult to crystallize lactic acid owing to the instability of the crystals, which are very hygroscopic. Due to this hygroscopicity, and due to the separation method used in the classical crystallization process, there is a liquid phase at the surface of the crystals. Further, the handling of the crystal is difficult because when the crystals contact air, they absorb water, increasing the amount of liquid phase present at the crystal surface.
These and other deficiencies are overcome using the products and methods of the present invention, as described below.